As shown in FIG. 1, the conventional illumination structure of the aquarium comprises a lampshade 10, a reflection plate 20, lamps 30, and at least a ballast 40, wherein the light emitted from the lamps 30 is reflected and focused inside the aquarium by the reflection plate 20 for illumination. The general illumination structure comprises the ballast 40 locked thereon. When the ballast 40 is broken, the consumers must spend much more time on the change of the broken ballast 40. Accordingly, in reality, it is very inconvenient for the manufacturers to make the ballast.